Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
F = [list(input()) for _ in range(H)]
cnt = 0
for i in range(H):
    for j in range(W):
        if F[i][j] == '.':
            cnt += 1


que = [[0, 0, 0]]
flag = True

while len(que) > 0 and flag:
    sp = que.pop(0)
    y, x, c = sp[0], sp[1], sp[2]
    for dy, dx in [[1,0], [-1,0], [0,1], [0,-1]]:
        if 0 <= y+dy < H and 0 <= x+dx < W and F[y+dy][x+dx] == ".":
            F[y+dy][x+dx] = c+1
            que.append([y+dy, x+dx, c+1])
            if y+dy == H-1 and x+dx == W-1:
                flag = False

if flag:
    print(-1)
else:
    print(cnt-F[H-1][W-1]-1)